The invention relates to a voice prosthesis.
As a result of different diseases the larynx of the diseased must sometimes be removed in an operation. In connection with such operations there must also be made a so called tracheostoma or an artificial tracheostoma fistula into the trachea so as to make possible breathing. Food stuff is taken in through the esophagus which is completely separated from the trachea.
Due to the measures mentioned above the ability of speech is lost. To some extent restore the ability of speech it is possible, by means of an operation, to open a fistula between the esophagus and the trachea to direct air to the oral cavity. However, said fistula must always be closed, except when air is admitted into the pharynx, because food stuff and liquids must be prevented from entering the trachea and further into the lungs.
To make it possible to open and close said fistula a so called voice prosthesis functioning as a one-way valve is inserted in said fistula. Said one-way valve permits air to pass from the trachea to the esophagus when a certain opening pressure has been reached in the trachea, but has to be completely closed in the reverse direction.
A voice prosthesis of this type is disclosed in U.S. Pat. No. 4,610,691. Said voice prosthesis includes a cylindrical housing having an inlet opening and an outlet opening and is mounted in such a way that said inlet opening opens into the trachea and said outlet opening opens into said esophagus. Said outlet opening is provided with a one-way valve in form of a perpendicular membrane hingedly mounted within the housing. Throughout the complete housing is a boring which at the point where said membrane is hinched is provided with a radially extending rim functioning as a sealing structure to said membrane. The inner diameter of said boring is substantially reduced at the position of said rim resulting in a decreased flow capacity of said prosthesis. The chosen type of valve results in a low opening pressure but the assembling of said prosthesis is complicated and the requirements for assembling are very high to minimize the risk that said membrane falls off, and also to insure that said membrane seals completely against said sealing structure.
A different form of voice prosthesis is put on the market by ENTERMED, P O Box 236, 3440 AI Woerden Hollland. Said prosthesis comprises a cylindrical web having an annular external flange in one end and a circular end wall formed with a slit in the other end. Said end wall extends radially from said web as an external flange and is curved in a convex shape. Said slit functioning as a valve extends as a diameter over said end wall and is normally closed. The prosthesis is inserted with said flange in trachea and said end wall in esophagus. In this type of voice prosthesis a very high opening pressure is required, and furthermore said valve is sensitive to influence from muscular movements in the esophagus, for instance at swallowing.
An object of the present invention is to overcome substantially the drawbacks and deficiencies of previously known voice prosthesis and to ensure a secure one-way function while maintaining a low opening pressure. Furthermore, the voice prosthesis according to the invention is comparatively easy to manufacture and to insert in the throat, and also permits a high flow in relation to the outer dimensions thereof. According to a further development a voice prosthesis has been accomplished which when mounted has a low tendency of rotating.